This invention relates to a method for determining a die profile for forming a metal part having a desired shape and associated methods. The shape of the die profile is made to compensate for the springback behavior of the materials that are used to form the desired product shape after forming, trimming or sub-assembly.
Die design, for many years, has been achieved by designers using trial and error, intuition and experience. This accumulated knowledge and experience is effective when dealing with a known material, such as mild steel. However, problems arise when new materials, such as high strength steel or aluminum are desired to be formed. When using these new materials, the old “rules of thumb” and the accumulated wisdom and experience of the designer sometimes prove to be ineffective. Furthermore, it is also time consuming and cost prohibitive to use this trial-and-error procedure for die development.
There are efforts now to make die design more of a “science” than an “art”. This involves using mathematical models and the mechanical properties of the metal which are used in the part, in combination with the formation process used to make the part, to give designers a better idea of the final design. With the new generation of automotive materials mentioned above, it is crucial to optimize die design, as uncompensated dies, if manufactured, are expensive and time-consuming to fix or replace and to minimize part springback to within acceptable tolerances. For example, it is estimated, for some dies, that “tool recuts” can cost more than a half-million dollars. It has been known that some complicated dies have to be recut five or more times. Obviously, this is a large cost item that must be avoided.
What is needed, therefore, is a method of making a die for forming a desired metal part that compensates for springback. The die should produce metal parts within a stated tolerance in critical regions within the part surface, and should do so with zero or a minimum of “tool recuts”.